Abrasive element including low thermal expansion constituent

ABSTRACT

In an embodiment, an abrasive element is disclosed. The abrasive element includes an abrasive body having a plurality of superabrasive grains, and at least one interstitial material interstitially disposed within the plurality of superabrasive grains. The at least one interstitial material exhibits a negative coefficient of thermal expansion over a selected temperature range.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/655,185 filed on 18 Oct. 2012, which is a continuation of U.S.application Ser. No. 13/291,463 filed on 8 Nov. 2011 (now U.S. Pat. No.8,312,943 issued on 20 Nov. 2012), which is a continuation of U.S.application Ser. No. 12/389,882 filed on 20 Feb. 2009 (now U.S. Pat. No.8,074,748 issued on 13 Dec. 2011), the contents of which areincorporated herein, in their entirety, by this reference.

BACKGROUND

Wear-resistant, polycrystalline diamond compacts (“PDCs”) are utilizedin a variety of mechanical applications. For example, PDCs are used indrilling tools (e.g., cutting elements, gage trimmers, etc.), machiningequipment, bearing apparatuses, wire-drawing machinery, and in othermechanical apparatuses.

PDCs have found particular utility as superabrasive cutting elements inrotary drill bits, such as roller-cone drill bits and fixed-cutter drillbits. A PDC cutting element typically includes a superabrasive diamondlayer commonly known as a diamond table. The diamond table is formed andbonded to a substrate using a high-pressure/high-temperature (“HPHT”)process. The PDC cutting element may also be brazed directly into apreformed pocket, socket, or other receptacle formed in a bit body. Thesubstrate may often be brazed or otherwise joined to an attachmentmember, such as a cylindrical backing. A rotary drill bit typicallyincludes a number of PDC cutting elements affixed to the bit body. It isalso known that a stud carrying the PDC may be used as a PDC cuttingelement when mounted to a bit body of a rotary drill bit bypress-fitting, brazing, or otherwise securing the stud into a receptacleformed in the bit body.

Conventional PDCs are normally fabricated by placing a cemented-carbidesubstrate into a container with a volume of diamond particles positionedon a surface of the cemented-carbide substrate. A number of suchcontainers may be loaded into an HPHT press. The substrate(s) and volumeof diamond particles are then processed under HPHT conditions in thepresence of a catalyst material that causes the diamond particles tobond to one another to form a matrix of bonded diamond grains defining apolycrystalline diamond (“PCD”) table. The catalyst material is often ametal-solvent catalyst (e.g., cobalt, nickel, iron, or alloys thereof)that is used for promoting intergrowth of the diamond particles.

In one conventional approach, a constituent of the cemented-carbidesubstrate, such as cobalt from a cobalt-cemented tungsten carbidesubstrate, liquefies and sweeps from a region adjacent to the volume ofdiamond particles into interstitial regions between the diamondparticles during the HPHT process. The cobalt acts as a catalyst topromote intergrowth between the diamond particles, which results information of a matrix of bonded diamond grains having diamond-to-diamondbonding therebetween, with interstitial regions between the bondeddiamond grains being occupied by the solvent catalyst.

The presence of the solvent catalyst in the PCD table is believed toreduce the thermal stability of the PCD table at elevated temperatures.For example, the difference in thermal expansion coefficient between thediamond grains and the solvent catalyst is believed to lead to chippingor cracking of the PCD table during drilling or cutting operations,which consequently can degrade the mechanical properties of the PCDtable or cause failure. Additionally, some of the diamond grains canundergo a chemical breakdown or back-conversion to graphite viainteraction with the solvent catalyst. At elevated high temperatures,portions of diamond grains may transform to carbon monoxide, carbondioxide, graphite, or combinations thereof, causing degradation of themechanical properties of the PCD table.

One conventional approach for improving the thermal stability of PDCs isto at least partially remove the solvent catalyst from the PCD table ofthe PDC by acid leaching. In another conventional approach for forming aPDC, a sintered PCD table may be separately formed and then leached toremove the solvent catalyst from interstitial regions between bondeddiamond grains. The leached PCD table may be simultaneously HPHT bondedto a cemented-carbide substrate and infiltrated with silicon in aseparate HPHT process. The silicon may infiltrate the interstitialregions of the leached PCD table from which the solvent catalyst hasbeen leached and react with the diamond grains to form silicon carbide.However, pure silicon may reduce the strength of the bond between thePCD table and the cemented-carbide substrate, and cause other processingproblems.

Despite the availability of a number of different PDCs, manufacturersand users of PDCs continue to seek PDCs that exhibit improved toughness,wear resistance, and/or thermal stability.

SUMMARY

Embodiments of the invention relate to thermally-stable PCD elements,PDCs, and methods of fabricating such PCD elements and PDCs. In anembodiment, a PCD element includes a PCD body comprising bonded diamondgrains defining a plurality of interstitial regions. The PCD bodyfurther includes a first volume having a first portion of theinterstitial regions and a second volume having a second portion of theinterstitial regions. An infiltrant is disposed in the first portion ofthe interstitial regions of the first volume and the second portion ofthe interstitial regions of the second volume is substantially free ofthe infiltrant. The infiltrant comprises a glass, a glass-ceramic, athermal decomposition reaction product of silicone, silicone, a ceramichaving a negative coefficient of thermal expansion, or combinationsthereof.

In an embodiment, a PDC includes a substrate and a thermally-stable PCDtable bonded to the substrate. The PCD table includes bonded diamondgrains defining a plurality of interstitial regions. The PCD tablefurther includes a first volume remote from the substrate having aninfiltrant disposed interstitially between the bonded diamond grainsthereof and a second volume adjacent to the substrate having ametal-solvent catalyst disposed interstitially between the bondeddiamond grains thereof. The infiltrant comprises a glass, aglass-ceramic, a thermal decomposition reaction product of silicone,silicone, a ceramic having a negative coefficient of thermal expansion,or combinations thereof.

In an embodiment, a method of manufacturing a thermally-stable PCDelement includes positioning an infiltrant material adjacent to asurface of an at least partially leached PCD body including a pluralityof interstitial regions. The infiltrant material includes a glass,silicone, a ceramic having a negative coefficient of thermal expansion,or combinations thereof. The method further includes infiltrating atleast a portion of the infiltrant material through the surface and intoonly a portion of the interstitial regions of the at least partiallyleached PCD body. In one embodiment, a PDC may be fabricated by placingthe at least partially leached PCD table between the substrate and theinfiltrant material, and subjecting the combination to an HPHT process.

In an embodiment, a method of forming a thermally-stable PDC includesproviding a PDC comprising an at least partially leached PCD tableincluding a plurality of interstitial regions and bonded to a substrate.The method further includes infiltrating at least a portion of theinterstitial regions of the at least partially leached PCD table with aninfiltrant material comprising a glass, silicone, a ceramic having anegative coefficient of thermal expansion, or combinations thereof.

Other embodiments include applications utilizing the disclosed PCDelements and PDCs in various articles and apparatuses, such as rotarydrill bits, bearing apparatuses, wire-drawing dies, machining equipment,and other articles and apparatuses.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate several embodiments of the invention, whereinidentical reference numerals refer to identical elements or features indifferent views or embodiments shown in the drawings.

FIG. 1 is a cross-sectional view of an embodiment of a thermally-stablePCD element.

FIG. 2 is a cross-sectional view of an assembly to be processed underHPHT conditions or using a hot isostatic pressing (“HIP”) process toform the PCD element shown in FIG. 1 according to an embodiment ofmethod.

FIG. 3 is a cross-sectional view of an embodiment of a thermally-stablePDC.

FIG. 4 is a cross-sectional view of an assembly to be HPHT processed toform the PDC shown in FIG. 3 according to an embodiment of method.

FIGS. 5A through 5D are cross-sectional views at various stages during amethod of fabricating the PDC shown in FIG. 3 according to an embodimentof method.

FIG. 6A is an isometric view of an embodiment of a rotary drill bit thatmay employ one or more of the disclosed PDC/PCD element embodiments.

FIG. 6B is a top elevation view of the rotary drill bit shown in FIG.6A.

FIG. 7 is an isometric cut-away view of an embodiment of athrust-bearing apparatus that may utilize one or more of the disclosedPDC/PCD element embodiments.

FIG. 8 is a schematic isometric cut-away view of an embodiment of asubterranean drilling system including the thrust-bearing apparatusshown in FIG. 7.

FIG. 9 is a side cross-sectional view of an embodiment of a wire-drawingdie that employs a PDC/PCD element fabricated in accordance with theprinciples described herein.

DETAILED DESCRIPTION

Embodiments of the invention relate to thermally-stable PCD elements,PDCs, and methods of fabricating such PCD elements and PDCs. Thedisclosed PCD elements comprise a first volume including a glass, aglass-ceramic, silicone, a thermal decomposition reaction product ofsilicone, a ceramic having a negative coefficient of thermal expansion,or combinations thereof to provide a thermally-stable working region,and a second volume that has been infiltrated with a metal-solventcatalyst for bonding to a substrate or a braze alloy for bonding to amatrix-type bit body of a rotary drill bit. The PCD elements and PDCsdisclosed herein may be used in a variety of applications, such asrotary drill bits, bearing apparatuses, wire-drawing dies, machiningequipment, and other articles and apparatuses.

FIG. 1 is a cross-sectional view of an embodiment of a thermally-stablePCD element 100 that may be used as PCD cutting element. The PCD element100 comprises a PCD body 102 including a plurality of bonded diamondgrains having diamond-to-diamond bonding therebetween. The plurality ofbonded diamond grains defines a plurality of interstitial regions. ThePCD body 102 includes a working upper surface 104 and an opposing backsurface 106. The PCD body 102 includes a first volume 108 having a firstportion of the interstitial regions, with the first volume 108 extendingfrom the upper surface 104 to an intermediate depth d within the PCDbody 102. The PCD body 102 includes a second volume 110 having a secondportion of the interstitial regions, with the second volume 110extending inwardly from the back surface 106. Although the upper surface104 is illustrated as being substantially planar, the upper surface maybe nonplanar (e.g., convex or concave) and a working region of the PCDbody 102 may include peripheral portions of the first volume 108.

In an embodiment, the intermediate depth d to which the first volume 108extends may be about the entire thickness of the PCD body 102. Inanother embodiment, the intermediate depth d may be about 50 μm to about500 μm, such as about 200 μm to about 400 μm.

An infiltrant, including a glass, a glass-ceramic, silicone, a thermaldecomposition reaction product of silicone, a ceramic having a negativecoefficient of thermal expansion, or combinations thereof, is disposedin the first portion of the interstitial regions of the PCD body 102.The infiltrant is generally non-catalytic relative to diamond so that atelevated temperatures the infiltrant does not promote chemical breakdownor back-conversion of the diamond grains to graphite, carbon monoxide,and/or carbon dioxide, which results in degradation of the mechanicalproperties of the PCD element 100. The interstitial regions of thesecond volume 110 of the PCD body 102 may be substantially free of theinfiltrant.

Suitable glasses for the infiltrant include, but are not limited to, asilicate glass, a borate glass, a phosphate glass, a borosilicate glass,and combinations of any of the foregoing glasses. For example, theinfiltrant may comprise sodium silicate, zirconium silicate, lithiumsilicate, sodium borosilicate, zirconium borosilicate, lithiumborosilicate, lithium aluminosilicate, or combinations thereof. In someembodiments, any of the foregoing glasses may be reinforced with afiller made from ceramic particles. For example, the ceramic particlesmay include, but are not limited to, boron nitride particles, titaniumdiboride particles, zirconium oxide particles, and combinations of theforegoing ceramic particles.

Suitable glass-ceramics for the infiltrant include, but are not limitedto, a silicate glass, a borate glass, a phosphate glass, a borosilicateglass, and combinations of any of the foregoing glasses that includebeta spodumene (“LiAlSi₂O₆”) and/or beta eucryptite (“LiAlSi₄O₁₀”) as aconstituent. Other glass-ceramics include a silicate glass, a borateglass, a phosphate glass, a borosilicate glass, an aluminosilicateglass, and combinations of any of the foregoing glasses that have beenpartially crystallized.

The infiltrant may also include or may be made from a ceramic having anegative coefficient of thermal expansion. One suitable ceramic having anegative coefficient of thermal expansion is zirconium tungstate, whichcontracts continuously over a temperature range from −272° C. to about775° C. Previously-mentioned ceramics having a negative coefficient ofthermal expansion are beta spodumene and beta eucryptite. Furthermore,combinations of zirconium tungstate, beta spodumene, and beta eucryptitemay also be employed. By providing an infiltrant that exhibits anegative to a small positive coefficient of thermal expansion, thermalstresses and/or thermal damage (e.g., breaking diamond-to-diamond bonds)may be reduced as the temperature of the PCD element 100 increasesduring use (e.g., during cutting a subterranean formation duringdrilling) compared to when the infiltrant is metallic, such as ametal-solvent catalyst.

The infiltrant occupying the first portion of the interstitial regionsof the first volume 108 may also include silicone, a thermaldecomposition reaction product of silicone, or combinations thereof. Aswill become apparent from reading the following description of methodsfor fabricating the PCD element 100, the thermal decomposition reactionproduct of silicone is a by-product of a silicone-based infiltrant thathas been infiltrated into the PCD body 102 during a process at atemperature sufficient to at least partially thermally decompose thesilicone-based infiltrant, such as an HPHT process or a HIP process.

The second volume 110 of the PCD body 102 is substantially free of theinfiltrant. Depending upon the particular application for the PCDelement 100, the second portion of the interstitial regions of thesecond volume 110 may include a metal-solvent catalyst for bonding to asubstrate (not shown) or a braze alloy used to braze the second volume110 to a matrix-type bit body (not shown) of a rotary drill bit.

FIG. 2 is a cross-sectional view of an assembly 200 to be processedunder HPHT conditions or using a HIP process to form the PCD element 100shown in FIG. 1 according to an embodiment of method. Referring to FIG.2, an at least partially leached PCD body 202 may be provided thatincludes the upper surface 104 and the opposing back surface 106. The atleast partially leached PCD body 202 includes a plurality of bondeddiamond grains defining a plurality of interstitial regions that werepreviously occupied by a metal-solvent catalyst (e.g., cobalt, nickel,iron, or alloys thereof) used to sinter the diamond particles. Theplurality of interstitial regions forms a network of at least partiallyinterconnected pores that extend between the upper surface 104 and theback surface 106.

A layer 204 of infiltrant material may be positioned adjacent to theupper surface 104 to form the assembly 200, such as by coating the uppersurface 104 with the infiltrant material or disposing the infiltrantmaterial in the bottom of a container and placing the at least partiallyleached PCD body 202 in the container and in contact with the infiltrantmaterial. In some embodiments, the infiltrant material of the layer 204may be in particulate form, a solid, in a liquid solution, a paste, orany other form that is capable of infiltrating into the interstitialregions of the at least partially leached PCD body 202.

Suitable infiltrant materials for the layer 204 include high-temperaturespecialty coatings commercially available from Aremco of Valley Cottage,N.Y. For example, Aremco-Seal™ 613 and 617 are two suitable glass-basedhigh-temperature specialty coatings commercially available from Aremco.As another example, Aremco-Cerama-Dip™ 538N is a suitable zirconiumsilicate-based high-temperature specialty coating commercially availablefrom Aremco. Another suitable high-temperature specialty coatingcommercially available from Aremco is Aremco-Seal™ 529, which is asilicone-based coating. Any of the foregoing high-temperature specialtycoatings commercially available from Aremco may be brushed onto theupper surface 104 of the at least partially leached PCD body 202 and/orbrushed into a container in which the at least partially leached PCDbody 202 is disposed. Other suitable infiltrant materials include, butare not limited to, glass powders, such as particles of sodium silicate,zirconium silicate, lithium silicate, sodium borosilicate, zirconiumborosilicate, lithium borosilicate, lithium aluminosilicate, andmixtures thereof.

The at least partially leached PCD body 202 and the layer 204 ofinfiltrant material may be placed in a pressure transmitting medium,such as a refractory metal can embedded in pyrophyllite or other gasketmedium. The pressure transmitting medium, including the at leastpartially leached PCD body 202 and layer 204 of infiltrant material, maybe subjected to an HPHT process using an ultra-high pressure press tocreate temperature and pressure conditions at which diamond is stable.The temperature of the HPHT process may be at least about 1000° C.(e.g., about 1200° C. to about 1600° C.) and the pressure of the HPHTprocess may be at least 4.0 GPa (e.g., about 5.0 GPa to about 8.0 GPa)for a time sufficient to infiltrate the at least partially leached PCDbody 202 with the infiltrant material. For example, the pressure of theHPHT process may be about 5 GPa to about 7 GPa and the temperature ofthe HPHT process may be about 1150° C. to about 1400° C. (e.g., about1200° C. to about 1300° C.).

During the HPHT process, infiltrant material from the layer 204infiltrates into the first volume 108 of the at least partially leachedPCD body 202 generally to the intermediate depth d to fill a firstportion of the interstitial regions thereof and form the PCD element 100as illustrated in FIG. 1. The first portion of first volume 108 of thePCD body 202 extends from the upper surface 104 to the intermediatedepth d therewithin. The amount of infiltrant material in the layer 204and the HPHT process conditions (e.g., time, temperature, and/orpressure) are selected so that the infiltrant material only infiltratesinto the first volume 108 of the at least partially leached PCD body 202to the intermediate depth d. The second volume 110 of the infiltratedPCD body 202 remains substantially free of the infiltrant.

The HPHT process may also chemically modify the infiltrant material ofthe layer 204. For example, various solvents included in the infiltrantmaterial may evaporate at the high temperature employed in the HPHTprocess. Some of the glass-based infiltrant materials may partiallycrystallize to form a glass-ceramic during the HPHT process. When theinfiltrant material is a silicone-based material, the resultantinfiltrant in the first volume 108 may include silicone, a thermaldecomposition reaction product of silicone formed as a result of thehigh-temperature employed in the HPHT process, or combinations thereof.

As discussed with respect to FIG. 1, if desired, the PCD element 100so-formed may be brazed to another structure, such as a matrix-type bitbody of a rotary drill bit, using a brazing process. In such anembodiment, a suitable braze alloy may be placed between the PCD element100 and the bit body, and subjected to a braze cycle to cause the brazealloy to melt and infiltrate into the second portion of the interstitialregions in the second volume 110 of the PCD element 100. Upon cooling astrong brazed joint may be formed due to the metallurgical bond betweenthe second volume 110 of the PCD element 100 and the bit body.

The at least partially leached PCD body 202 shown in FIG. 2 may befabricated by subjecting a plurality of diamond particles to an HPHTsintering process in the presence of a metal-solvent catalyst (e.g.,cobalt, nickel, iron, or alloys thereof) to facilitate intergrowthbetween the diamond particles and form a PCD body comprised of bondeddiamond grains that exhibit diamond-to-diamond bonding therebetween. Forexample, the metal-solvent catalyst may be mixed with the diamondparticles or infiltrated from a metal-solvent catalyst foil or powderadjacent to the diamond particles. The bonded diamond grains defineinterstitial regions, with the metal-solvent catalyst disposed withinthe interstitial regions. The diamond particles may exhibit asingle-mode diamond particle size distribution, or a bimodal or greaterdiamond particle size distribution. The as-sintered PCD body may beleached by immersion in an acid, such as aqua regia, nitric acid,hydrofluoric acid, or subjected to another suitable process to remove atleast a portion of the metal-solvent catalyst from the interstitialregions of the PCD body and form the at least partially leached PCD body202. For example, the as-sintered PCD body may be immersed in the acidfor about 2 to about 7 days (e.g., about 3, 5, or 7 days) or for a fewweeks (e.g., about 4 weeks) depending on the process employed.

The plurality of diamond particles sintered to form the at leastpartially leached PCD body 202 may exhibit one or more selected sizes.The one or more selected sizes may be determined, for example, bypassing the diamond particles through one or more sizing sieves or byany other method. In an embodiment, the plurality of diamond particlesmay include a relatively larger size and at least one relatively smallersize. As used herein, the phrases “relatively larger” and “relativelysmaller” refer to particle sizes determined by any suitable method,which differ by at least a factor of two (e.g., 40 μm and 20 μm). Moreparticularly, in various embodiments, the plurality of diamond particlesmay include a portion exhibiting a relatively larger size (e.g., 100 μm,90 μm, 80 μm, 70 μm, 60 μm, 50 μm, 40 μm, 30 μm, 20 μm, 15 μm, 12 μm, 10μm, 8 μm) and another portion exhibiting at least one relatively smallersize (e.g., 30 μm, 20 μm, 10 μm, 15 μm, 12 μm, 10 μm, 8 μm, 4 μm, 2 μm,1 μm, 0.5 μm, less than 0.5 μm, 0.1 μm, less than 0.1 μm). In anotherembodiment, the plurality of diamond particles may include a portionexhibiting a relatively larger size between about 40 μm and about 15 μmand another portion exhibiting a relatively smaller size between about12 μm and 2 μm. Of course, the plurality of diamond particles may alsocomprise three or more different sizes (e.g., one relatively larger sizeand two or more relatively smaller sizes) without limitation.

Instead of infiltrating the at least partially leached PCD body 202 inan HPHT process, in another embodiment, the infiltrant material of thelayer 204 may be infiltrated into the at least partially leached PCDbody 202 using a HIP process that employs significantly lower pressure.In such an embodiment, the temperature of the HIP process should be keptsufficiently low and/or the process time sufficiently short so that thediamond grains of the at least partially leached PCD body 202 are notsignificantly degraded.

FIG. 3 is a cross-sectional view of an embodiment of a PDC 300. The PDC300 includes a thermally-stable PCD table 302 having a working uppersurface 304 and an opposing interfacial surface 306. The interfacialsurface 306 of the PCD table 302 is bonded to a substrate 308. Thesubstrate 308 may include, without limitation, cemented carbides, suchas tungsten carbide, titanium carbide, chromium carbide, niobiumcarbide, tantalum carbide, vanadium carbide, or combinations thereofcemented with iron, nickel, cobalt, or alloys thereof. For example, inone embodiment, the substrate 308 comprises cobalt-cemented tungstencarbide. Although the interfacial surface 306 of the PCD table 302 isdepicted in FIG. 3 as being substantially planar, the interfacialsurface 306 may exhibit a selected nonplanar topography.

The PCD table 302 includes a plurality of bonded diamond grains havingdiamond-to-diamond bonding therebetween. The plurality of bonded diamondgrains defines a plurality of interstitial regions. The PCD table 302includes a first volume 310 remote from the substrate 308 that extendsfrom the upper surface 304 to an indeterminate depth d within the PCDtable 302. The first volume 310 includes a first portion of theinterstitial regions. A second volume 312 of the PCD table 302 adjacentto the substrate 308 includes a second portion of the interstitialregions.

In an embodiment, the intermediate depth d to which the first volume 310extends may be about the entire thickness of the PCD table 302. Inanother embodiment, the intermediate depth d may be about 50 μm to about500 μm, such as about 200 μm to about 400 μm.

Any of the previously described infiltrants, such as a glass, aglass-ceramic, silicone, a thermal decomposition reaction product ofsilicone, a ceramic having a negative coefficient of thermal expansion,or combinations thereof may occupy the first portion of the interstitialregions of the PCD table 302. Because the infiltrant is generallynon-catalytic relative to diamond, the first volume 310 of the PCD table302 provides a relatively thermally-stable working region compared tothe second volume 312. Although PCD table 302 is illustrated as having asubstantially planar upper surface 304, the upper surface may benonplanar (e.g., convex or concave) and include peripheral portions ofthe first volume 310. The second volume 312 of the PCD table 302 may beinfiltrated with a metal-solvent catalyst infiltrated from the substrate308, such as cobalt from a cobalt cemented tungsten carbide substrate,or other source. The infiltrated metal-solvent catalyst from thesubstrate 308 provides a strong metallurgical bond between theinterfacial surface 306 of the PCD table 302 and the substrate 308.

In one embodiment, the PCD table 302 may be a pre-sintered PCD tablethat is bonded to the substrate 308 subsequent to being formed. Inanother embodiment, the PCD table 302 may be integrally formed with thesubstrate 308 by placing diamond powder adjacent to the substrate 308,subjecting the combination to an HPHT process, and substantiallyremoving metal-solvent catalyst in the PCD table so-formed using aleaching process.

FIG. 4 is a cross-sectional view of an assembly 404 to be HPHT processedto form the PDC shown in FIG. 3 according to an embodiment of method. Anat least partially leached PCD table 400 may be positioned between alayer 402 of infiltrant material and the substrate 308 to form anassembly 404. The at least partially leached PCD table 400 may exhibitthe same or similar structure as the at least partially leached PCD body202 shown in FIG. 2 and may fabricated in the same fashion. Theinfiltrant material may be selected from one or more of the infiltrantmaterials used for the infiltrant material of the layer 204 shown inFIG. 2. The layer 402 may be applied to the upper surface 304 of the atleast partially leached PCD table 402, and the interfacial surface 306of the at least partially leached PCD table 400 may be positionedadjacent to the substrate 308. The assembly 404 may be enclosed in asuitable pressure transmitting medium and subjected to an HPHT processto form the PDC 300 (FIG. 3) using the same or similar HPHT conditionspreviously discussed with respect to HPHT processing the assembly 200shown in FIG. 2.

During the HPHT process, the lower melting infiltrant material of thelayer 402 infiltrates into a first portion of the interstitial regionsof the at least partially leached PCD table 400. Depending upon theparticular infiltrant material employed, any of the previously describedinfiltrants (e.g., a glass, a glass-ceramic, a silicone, a thermaldecomposition reaction product of silicone, a ceramic having a negativecoefficient of thermal expansion, or combinations thereof) may occupythe first portion of the interstitial regions of the at least partiallyleached PCD table 400. The metal-solvent catalyst of the substrate 308liquefies at a higher temperature, and infiltrates subsequent toinfiltration of the infiltrant material of the layer 402 and into asecond portion of the interstitial regions of the at least partiallyleached PCD table 400 so that a strong metallurgical bond is formedbetween the substrate 308 and the interfacial surface 306 upon cooling.The infiltrant that occupies the first portion of the interstitialregions substantially blocks or at least limits further infiltrationinto the at least partially leached PCD table 400 by the metal-solventcatalyst.

In an embodiment, when the infiltrant material of the layer 402 is madepredominately from a glass (e.g., a borosilicate-based glass) and thesubstrate 308 is a cobalt-cemented carbide substrate, the infiltrantmaterial flows and infiltrates into the at least partially leached PCDtable 400 at or slightly above about 800° C. and cobalt-cemented carbidesubstrate from the substrate 308 liquefies and sweeps into the at leastpartially leached PCD table 400 at around about 1490° C.

In an embodiment, the metal-solvent catalyst may also be provided froman intermediate layer disposed between the at least partially leachedPCD table 400 and the substrate 308. The intermediate layer may includeany of the aforementioned metal-solvent catalysts. For example, theintermediate layer may include a plurality of metal-solvent catalystparticles, or a thin foil or plate made from the metal-solvent catalyst.

In other embodiments, the at least partially leached PCD table 400 isinfiltrated with the infiltrant material from the layer 402 to aselected depth in a first HPHT or HIP process and is subsequently bondedto the substrate 308 by brazing, using a separate HPHT bonding process,or another suitable joining technique, without limitation.

FIGS. 5A through 5D are cross-sectional views at various stages during amethod of fabricating the PDC 300 shown in FIG. 3 according to anotherembodiment of method. Referring to FIG. 5A, a plurality of diamondparticles (i.e., diamond powder) may be placed adjacent to the substrate308. Referring to FIG. 5B, subjecting the diamond particles 500 and thesubstrate 308 to an HPHT process sweeps metal-solvent catalyst from thesubstrate 308 into the diamond particles 500 to catalyze formation of aPCD table 502 therefrom that is integrally formed and bonded to thesubstrate 308. The PCD table 502 comprises bonded diamond grainsdefining a plurality of interstitial regions in which the swept-inmetal-solvent catalyst is disposed.

Referring to FIG. 5C, the metal-solvent catalyst interstitially disposedbetween the bonded diamond grains of the PCD table 502 may besubstantially removed to a selected depth d using a leaching process toform an at least partially leached region 504 remote from the substrate308. For example, the PCD table 502 may be exposed to an acid, such asaqua regia, nitric acid, hydrofluoric acid, or subjected to anothersuitable process to substantially remove the metal-solvent catalyst andform the at least partially leached region 504. Region 506 of the PCDtable 502 adjacent to the substrate 308 still includes the swept-inmetal-solvent catalyst from the substrate 308 disposed interstitiallybetween bonded diamond grains.

Referring to FIG. 5D, a layer 402 of infiltrant material may be placedadjacent to a working upper surface 508 of the PCD table 502 andinfiltrated into the interstitial regions of the at least partiallyleached region 504 using another HPHT process or a HIP process to formthe PDC 300 shown in FIG. 3. The temperature of the HPHT or HIP processmay be selected to be less than a temperature at which the metal-solventcatalyst in the region 506 of the PCD table 502 or the substrate 308partially liquefies to prevent re-infiltration of the at least partiallyleached region 504 with the metal-solvent catalyst.

The following working examples set forth various formulations forforming PDCs. In the following working examples, the thermal stabilityof conventional working examples 1 through 3 is compared to the thermalstability of working examples 4 through 7 of the invention.

Comparative Example 1

A conventional PDC was obtained that was fabricated by placing a layerof diamond particles having an average particle size of about 19 μmadjacent to a cobalt-cemented tungsten carbide substrate. The layer andsubstrate were placed in a container assembly. The container assemblyincluding the layer and substrate therein were subjected to HPHTconditions in an HPHT press at a temperature of about 1400° C. and apressure of about 5 GPa to about 8 GPa to form a conventional PDCincluding a PCD table integrally formed and bonded to the substrate.Cobalt was infiltrated into the layer of diamond particles from thesubstrate catalyzing the formation of the PCD table. The thickness ofthe PCD table of the PDC was about 0.095 inch and an about 0.011-inchchamfer was machined in the PCD table.

The thermal stability of the PCD table of the conventional PDC so-formedof comparative example 1 was evaluated by measuring the distance cut ina Barre granite workpiece prior to failure, without using coolant, in avertical turret lathe test. The distance cut is consideredrepresentative of the thermal stability of the PCD table. The testparameters were a depth of cut for the PDC of about 1.27 mm, a back rakeangle for the PDC of about 20 degrees, an in-feed for the PDC of about1.524 mm/rev, a cutting speed of the workpiece to be cut of about 1.78msec, and the workpiece had an outer diameter of about 914 mm and aninner diameter of about 254 mm. The conventional PDC of comparativeexample 1 was able to cut a distance of about 1715 linear feet in theworkpiece prior to failure.

Comparative Example 2

A PDC was obtained that was fabricated as performed in comparativeexample 1. The thickness of the PCD table of the PDC was about 0.09155inch and an about 0.01285-inch chamfer was machined in the PCD table.Then, the PCD table was acid leached to a depth of about 87 μm. Thethermal stability of the PCD table of the conventional PDC so-formed ofcomparative example 2 was evaluated by measuring the distance cut priorto failure in the same Barre granite workpiece used to test comparativeexample 1 and using the same test parameters, without using coolant, ina vertical turret lathe test. The conventional PDC of comparativeexample 2 was able to cut a distance of about 3453 linear feet in theworkpiece prior to failure.

Comparative Example 3

A PDC was obtained that was fabricated as performed in comparativeexample 1. The thickness of the PCD table of the PDC was about 0.097inch and an about 0.0122-inch chamfer was machined in the PCD table. ThePCD table was acid leached to a depth of greater than about 200 μm. Thethermal stability of the PCD table of the conventional PDC so-formed ofcomparative example 3 was evaluated by measuring the distance cut priorto failure in the same Barre granite workpiece used to test comparativeexample 1 and using the same test parameters, without using coolant, ina vertical turret lathe test. The conventional PDC of comparativeexample 3 was able to cut a distance of about 8508 linear feet in theworkpiece prior to failure.

Example 4

A leached PDC was obtained that was fabricated as performed incomparative example 3. The thickness of the PCD table of the leached PDCwas 0.090 inch and a 0.0122-inch chamfer was machined in the PCD table.A layer of infiltrant material made from an Aremco-Seal™ 613 coating wasdisposed in the bottom of a container assembly. The leached PDC wasplaced in the container assembly, with the leached PCD table placedadjacent to the layer of Aremco-Seal™ 613 coating. The containerassembly including the layer of Aremco-Seal™ 613 coating and the leachedPDC therein was subjected to HPHT conditions in an HPHT press at atemperature of about 1200° C. and a pressure of about 5 GPa to about 8GPa to infiltrate the leached portion of the PCD table with theinfiltrant material from the layer. The thermal stability of theinfiltrated PCD table of the PDC so-formed of example 4 was evaluated bymeasuring the distance cut prior to failure in the same Barre graniteworkpiece used to test comparative example 1 and using the same testparameters, without using coolant, in a vertical turret lathe test. Theinfiltrated PCD table of the PDC of example 4 was able to cut a distanceof greater than 10,422 linear feet in the workpiece prior to failure,which was greater than the distance that the leached PDC of comparativeexample 3 was able to cut.

Example 5

A leached PDC was obtained that was fabricated as performed incomparative example 3. The thickness of the PCD table of the leached PDCwas about 0.089 inch and an about 0.0118-inch chamfer was machined inthe PCD table. A layer of infiltrant material made from an Aremco-Seal™613 coating was disposed in the bottom of a container assembly. Theleached PDC was placed in the container assembly, with the leached PCDtable placed adjacent to the layer of Aremco-Seal™ 613 coating. Thecontainer assembly including the layer of Aremco-Seal™ 613 coating andthe leached PDC therein was subjected to HPHT conditions in an HPHTpress at a temperature of about 1300° C. and a pressure of about 5 GPato about 8 GPa to infiltrate the leached portion of the PCD table withthe infiltrant material from the layer. The thermal stability of theinfiltrated PCD table of the PDC so-formed of example 5 was evaluated bymeasuring the distance cut prior to failure in the same Barre graniteworkpiece used to test comparative example 1 and using the same testparameters, without using coolant, in a vertical turret lathe test. Theinfiltrated PCD table of the PDC of example 5 was able to cut a distanceof about 4864 linear feet in the workpiece prior to failure, which wasgreater than the distances that the leached PCD tables of comparativeexamples 1 and 2 were able to cut.

Example 6

A leached PDC was obtained that was fabricated as performed incomparative example 3. The thickness of the PCD table of the leached PDCwas about 0.091 inch and an about 0.0118-inch chamfer was machined inthe PCD table. A layer of infiltrant material made from an Aremco-Seal™617 coating was disposed in the bottom of a container assembly. Theleached PDC was placed in the container assembly, with the leached PCDtable placed adjacent to the layer of Aremco-Seal™ 617 coating. Thecontainer assembly including the layer of Aremco-Seal™ 617 coating andthe leached PDC therein was subjected to HPHT conditions in an HPHTpress at a temperature of about 1300° C. and a pressure of about 5 GPato about 8 GPa to infiltrate the leached portion of the PCD table withthe infiltrant material from the layer. The thermal stability of theinfiltrated PCD table of the PDC so-formed of example 6 was evaluated bymeasuring the distance cut prior to failure in the same Barre graniteworkpiece used to test comparative example 1 and using the same testparameters, without using coolant, in a vertical turret lathe test. Theinfiltrated PCD table of the PDC of example 6 was able to cut a distanceof about 4030 linear feet in the workpiece prior to failure, which wasgreater than the distances that the leached PCD tables of comparativeexamples 1 and 2 were able to cut.

Example 7

A leached PDC was obtained that was fabricated as performed incomparative example 3. The thickness of the PCD table of the leached PDCwas about 0.091 inch and an about 0.0119-inch chamfer was machined inthe PCD table. A layer of infiltrant material made from an Aremco-Seal™617 coating was disposed in the bottom of a container assembly. Theleached PDC was placed in the container assembly, with the leached PCDtable placed adjacent to the layer of Aremco-Seal™ 617 coating. Thecontainer assembly including the layer of Aremco-Seal™ 617 coating andthe leached PDC therein was subjected to HPHT conditions in an HPHTpress at a temperature of about 1200° C. and a pressure of about 5 GPato about 8 GPa to infiltrate the leached portion of the PCD table withthe infiltrant material from the layer. The thermal stability of theinfiltrated PCD table of the PDC so-formed of example 6 was evaluated bymeasuring the distance cut prior to failure in the same Barre graniteworkpiece used to test comparative example 1 and using the same testparameters, without using coolant, in a vertical turret lathe test. Theinfiltrated PCD table of the PDC of example 7 was able to cut a distanceof about 7236 linear feet in the workpiece prior to failure, which wasgreater than the distances that the leached PCD tables of comparativeexamples 1 and 2 were able to cut.

The disclosed PCD element and PDC embodiments may be used in a number ofdifferent applications including, but not limited to, use in a rotarydrill bit (FIGS. 6A and 6B), a thrust-bearing apparatus (FIG. 7), asubterranean drilling system (FIG. 8), and a wire-drawing die (FIG. 9).The various applications discussed above are merely some examples ofapplications in which the PCD element and PDC embodiments may be used.Other applications are contemplated, such as employing the disclosed PCDelement and PDC embodiments in friction stir welding tools.

FIG. 6A is an isometric view and FIG. 6B is a top elevation view of anembodiment of a rotary drill bit 600. The rotary drill bit 600 includesat least one PDC configured according to any of the previously describedPDC embodiments. The rotary drill bit 600 comprises a bit body 602 thatincludes radially and longitudinally extending blades 604 having leadingfaces 606, and a threaded pin connection 608 for connecting the bit body602 to a drilling string. The bit body 602 defines a leading endstructure for drilling into a subterranean formation by rotation about alongitudinal axis 610 and application of weight-on-bit. At least one PDCcutting element, configured according to any of the previously describedPDC embodiments (e.g., the PDC 300 shown in FIG. 3), may be affixed tothe bit body 602. With reference to FIG. 6B, a plurality of PDCs 612 aresecured to the blades 604. For example, each PDC 612 may include a PCDtable 614 bonded to a substrate 616. More generally, the PDCs 612 maycomprise any PDC disclosed herein, without limitation. In addition, ifdesired, in some embodiments, a number of the PDCs 612 may beconventional in construction. Also, circumferentially adjacent blades604 define so-called junk slots 618 therebetween, as known in the art.Additionally, the rotary drill bit 600 may include a plurality of nozzlecavities 620 for communicating drilling fluid from the interior of therotary drill bit 600 to the PDCs 612.

In the illustrated embodiment shown in FIGS. 6A and 6B, each PDC 612 isshown as a compact having a polycrystalline diamond table bonded to asubstrate. However, in other embodiments, one or more of the PDCs 612may be replaced by a PCD element (e.g., the PCD element 100 shown inFIG. 1) that is brazed to the bit body 602. In such an embodiment, thebraze alloy infiltrates into and fills the interstitial regions of thesecond volume 110 of the PCD body 102 so that a strong metallurgicalbond is formed between the bit body 602 and the PCD element.

FIGS. 6A and 6B merely depict an embodiment of a rotary drill bit thatemploys at least one cutting element comprising a PDC or PCD elementfabricated and structured in accordance with the disclosed embodiments,without limitation. The rotary drill bit 600 is used to represent anynumber of earth-boring tools or drilling tools, including, for example,core bits, roller-cone bits, fixed-cutter bits, eccentric bits, bicenterbits, reamers, reamer wings, or any other downhole tool including PDCsor PCD elements, without limitation.

The PCD elements and PDCs disclosed herein (e.g., the PDC 300 shown inFIG. 3) may also be utilized in applications other than rotary drillbits. For example, the disclosed PCD element and PDC embodiments may beused in thrust-bearing assemblies, radial bearing assemblies,wire-drawing dies, artificial joints, machining elements, and heatsinks.

FIG. 7 is an isometric cut-away view of an embodiment of athrust-bearing apparatus 700, which may utilize any of the disclosed PDCembodiments as bearing elements. The thrust-bearing apparatus 700includes respective thrust-bearing assemblies 702. Each thrust-bearingassembly 702 includes an annular support ring 704 that may be fabricatedfrom a material, such as carbon steel, stainless steel, or anothersuitable material. Each support ring 704 includes a plurality ofrecesses (not labeled) that receives a corresponding bearing element706. Each bearing element 706 may be mounted to a corresponding supportring 704 within a corresponding recess by brazing, press-fitting, usingfasteners, or another suitable mounting technique. One or more, or allof bearing elements 706 may be configured according to any of thedisclosed PDC embodiments. For example, each bearing element 706 mayinclude a substrate 708 and a PCD table 710, with the PCD table 710including a bearing surface 712.

In use, the bearing surfaces 712 of one of the thrust-bearing assemblies702 bears against the opposing bearing surfaces 712 of the other one ofthe bearing assemblies 702. For example, one of the thrust-bearingassemblies 702 may be operably coupled to a shaft to rotate therewithand may be termed a “rotor.” The other one of the thrust-bearingassemblies 702 may be held stationary and may be termed a “stator.”

Referring to FIG. 8, the thrust-bearing apparatus 700 may beincorporated in a subterranean drilling system. FIG. 8 is a schematicisometric cut-away view of a subterranean drilling system 800 thatincludes at least one of the thrust-bearing apparatuses 700 shown inFIG. 7 according to another embodiment. The subterranean drilling system800 includes a housing 802 enclosing a downhole drilling motor 804(i.e., a motor, turbine, or any other device capable of rotating anoutput shaft) that is operably connected to an output shaft 806. A firstthrust-bearing apparatus 700 ₁ (FIG. 7) is operably coupled to thedownhole drilling motor 804. A second thrust-bearing apparatus 700 ₂(FIG. 7) is operably coupled to the output shaft 806. A rotary drill bit808 configured to engage a subterranean formation and drill a boreholeis connected to the output shaft 806. The rotary drill bit 808 is shownas a roller-cone bit including a plurality of roller cones 810. However,other embodiments may utilize different types of rotary drill bits, suchas a so-called “fixed-cutter” drill bit shown in FIGS. 6A and 6B. As theborehole is drilled, pipe sections may be connected to the subterraneandrilling system 800 to form a drill string capable of progressivelydrilling the borehole to a greater depth within the earth.

A first one of the thrust-bearing assemblies 702 of the thrust-bearingapparatus 700 ₁ is configured as a stator that does not rotate and asecond one of the thrust-bearing assemblies 702 of the thrust-bearingapparatus 700 ₁ is configured as a rotor that is attached to the outputshaft 806 and rotates with the output shaft 806. The on-bottom thrustgenerated when the drill bit 808 engages the bottom of the borehole maybe carried, at least in part, by the first thrust-bearing apparatus 700₁. A first one of the thrust-bearing assemblies 702 of thethrust-bearing apparatus 700 ₂ is configured as a stator that does notrotate and a second one of the thrust-bearing assemblies 702 of thethrust-bearing apparatus 700 ₂ is configured as a rotor that is attachedto the output shaft 806 and rotates with the output shaft 806. Fluidflow through the power section of the downhole drilling motor 804 maycause what is commonly referred to as “off-bottom thrust,” which may becarried, at least in part, by the second thrust-bearing apparatus 700 ₂.

In operation, drilling fluid may be circulated through the downholedrilling motor 804 to generate torque and effect rotation of the outputshaft 806 and the rotary drill bit 808 attached thereto so that aborehole may be drilled. A portion of the drilling fluid may also beused to lubricate opposing bearing surfaces of the bearing elements 706of the thrust-bearing assemblies 702.

FIG. 9 is a side cross-sectional view of an embodiment of a wire-drawingdie 900 that employs a PDC 902 fabricated in accordance with theteachings described herein. The PDC 902 includes an inner, annular PCDregion 904 comprising any of the PCD tables described herein that isbonded to an outer cylindrical substrate 906 that may be made from thesame materials as the substrate 308 shown in FIG. 3. The PCD region 904also includes a die cavity 908 formed therethrough configured forreceiving and shaping a wire being drawn. The wire-drawing die 900 maybe encased in a housing (e.g., a stainless steel housing), which is notshown, to allow for handling. In use, a wire 910 of a diameter d₁ isdrawn through die cavity 908 along a wire drawing axis 912 to reduce thediameter of the wire 910 to a reduced diameter d₂.

While various aspects and embodiments have been disclosed herein, otheraspects and embodiments are contemplated. The various aspects andembodiments disclosed herein are for purposes of illustration and arenot intended to be limiting. Additionally, the words “including,”“having,” and variants thereof (e.g., “includes” and “has”) as usedherein, including the claims, shall have the same meaning as the word“comprising” and variants thereof (e.g., “comprise” and “comprises”).

What is claimed is:
 1. An abrasive element, comprising: an abrasive bodyincluding: a plurality of superabrasive grains including a plurality ofdiamond grains; and at least one interstitial material interstitiallydisposed within the plurality of superabrasive grains, the at least oneinterstitial material including at least one ceramic exhibiting anegative coefficient of thermal expansion over a selected temperaturerange.
 2. The abrasive element of claim 1 wherein the at least oneceramic is selected from the group consisting of zirconium tungstate,beta spodumene, and beta eucryptite.
 3. The abrasive element of claim 1wherein the at least one ceramic comprises zirconium tungstate.
 4. Theabrasive element of claim 1 wherein the at least one ceramic comprisesbeta spodumene.
 5. The abrasive element of claim 1 wherein the at leastone ceramic comprises beta eucryptite.
 6. The abrasive element of claim1 wherein the selected temperature range is about −272° C. to about 775°C.
 7. The abrasive element of claim 1 wherein the plurality of diamondgrains exhibiting diamond-to-diamond bonding therebetween.
 8. Anabrasive element, comprising: an abrasive body including: a plurality ofsuperabrasive grains; and at least one metal tungstate interstitiallydisposed within the plurality of superabrasive grains, the at least onemetal tungstate exhibits a negative coefficient of thermal expansionover a selected temperature range.
 9. The abrasive element of claim 8wherein the at least one metal tungstate includes zirconium tungstate.10. The abrasive element of claim 8 wherein the selected temperaturerange is about −272° C. to about 775° C.
 11. The abrasive element ofclaim 8 wherein the plurality of superabrasive grains includes aplurality of diamond grains.
 12. The abrasive element of claim 8 whereinthe plurality of superabrasive grains includes diamond grains exhibitingdiamond-to-diamond bonding therebetween.
 13. A superabrasive abrasiveelement, comprising: an abrasive body including: a plurality of diamondgrains exhibiting diamond-to-diamond bonding therebetween and defining aplurality of interstitial regions; and at least one interstitialmaterial disposed in at least some of the plurality of interstitialregions, the at least one interstitial material including at least onemetal tungstate and at least one additional material different than theat least one metal tungstate.
 14. The superabrasive element of claim 13wherein the at least one metal tungstate includes zirconium tungstate.15. The superabrasive element of claim 13 wherein the at least oneinterstitial material exhibits a negative coefficient of thermalexpansion over a selected temperature range.
 16. The superabrasiveelement of claim 15 wherein the selected temperature range is about−272° C. to about 775° C.
 17. The superabrasive element of claim 13wherein the at least one additional material of the at least oneinterstitial material includes at least one of beta spodumene or betaeucryptite.